Combustor front assembly for a gas turbine

ABSTRACT

A combustor front assembly for a gas turbine power plant, wherein the combustor front assembly is provided with at least a through hole for allowing gas flow into a combustion chamber, the combustor front assembly having a combustor front plate with at least a through hole and with an outer surface outside the combustor chamber; a combustor front segment having a through hole and coupled with the outer surface of the combustor front plate so that the through hole of the front segment is aligned with the through hole of the front plate; wherein the combustor front segment is clamped in position and forced against the outer surface of the combustor front plate.

PRIORITY CLAIM

This application claims priority from European Patent Application No. 16190197.0 filed on Sep. 22, 2016, the disclosure of which is incorporated by reference.

FIELD OF THE INVENTION

The present invention relates to a combustor front assembly for a gas turbine power plant.

In particular, the present invention refers to an annular combustor front assembly suitable to be preferably associated with a plurality of EV burners.

Moreover, the present invention refers to a gas turbine power plant provided with the above combustor front assembly.

DESCRIPTION OF PRIOR ART

A gas turbine power plant (in the following only gas turbine) comprises, following the main gas flow, a compressor fed with air, one or more combustors fed with the compressed air wherein a fuel is injected, mixed to the air flow and burnt in order to generate an high pressure gas, and a turbine fed with the high pressure gas.

In the case of the gas turbine is provided with an annular combustor, the combustion chamber is an annular structure around the gas turbine axis. This annular combustion chamber is outwardly and inwardly delimited by side walls, upstream by a front assembly coupled with a plurality of burners and downstream by a hot gas discharge passage facing the turbine.

The terms outwardly/outer and inwardly/inner refer to the gas turbine axis. The terms upstream and downstream refer to the main gas flow direction.

An example of this kind of gas turbine is schematically represented in FIG. 1 wherein the reference M refers to the main gas flow direction. In particular, the gas turbine 1 comprises a casing 2 covering a rotor 3 able to rotate around an axis 4. On the upstream side, the gas turbine 1 comprises a compressor 5 for compressing air that flows into a plenum 6. Inside the plenum 6, the gas turbine 1 comprises an annular combustion chamber 7 arranged concentrically to the axis 4 and provided with an inner 13 and an outer shell 14. On the inlet side, the annular combustion chamber 7 comprises a combustor front assembly 8 that is ring-shaped around the axis 4. On the outlet side, the annular combustion chamber 7 comprises a hot gas passage 9 connected with the inlet of the turbine 10. FIG. 1 discloses a burner 11, in particular an EV-burner, coupled to the combustor front assembly 8. Of course, along the combustor front assembly 8 the gas turbine 1 comprises a plurality of burner 11 equally spaced. The gas leaves the burner and enters the annular combustion chamber 7 passing thought the combustor front assembly 8. A hot air flow 12 formed during the combustion reaches the turbine 10 passing through the above mentioned hot gas passage 9 at the outlet side of the annular combustion chamber 7. Into the turbine 10 the hot air flow expands performing rotating work on the axis 4. The combustion chamber 7 is preferably enclosed by an outer 15 and inner cooling shroud 16 in order to realize an outer 17 and inner cooling passage 18. In the cooling passages 17 18, cooling air flows in the opposite direction with respect to the hot gas flow 12 along the walls of the combustion chamber 7 into a combustor hood 19. From the combustor hood 19 the air flows into the burner 11 or, passing thought front cooling passages 20, directly into the combustion chamber 7.

As foregoing described, the burner disclosed in FIG. 1 is preferably a EV burner where EV stand for “enVironmental” burner. Alternatively, the burners can be AEV-burners where AEV stand for “Advanced EnVironmental”. This kind of burners is characterized by a very low NOx levels. For instance, EP0851172, EP2423597 and WO 2009/019113 disclose EV burners provided with a single or double cone and comprising a swirl generator and a mixing tube at the exit of a burner prior the combustion chamber. The mixing tube is configured to stabilize the swirl flow. Preferably, between the swirl generator and the mixing tube an EV burner comprises also a transition piece.

FIG. 2 shows an enlarged view of a portion of a combustor front assembly according to the prior art. In particular. As known, the combustor front assembly comprises a combustor front plate 32 that is ring-shaped around the gas turbine axis. The combustor front plate 32 can be arranged orthogonal with respect to the gas turbine axis 4 or inclined as disclosed in FIG. 1. The combustor front plate 32 comprises a plurality of through holes 21 equally spaced along the combustor front plate 32. These through holes 21 define a plurality of passages for the hot gas from the burners 11 to the annular combustion chamber 7. In particular, each through hole 21 of the front plate 32 is coupled with the relevant burner 11, preferably with the mixing tube in case of a EV burner. As disclosed in FIG. 2, on the front plate 32 the combustor front assembly comprises a plurality of combustor front segments 22 that are tile-shaped and cover, on the burner 11 side, the entire length of the front plate 32. Each front segment 22 comprises a through hole 23 that, once the segment 22 is coupled with the plate 32, is axially aligned with the front plate through hole 21. As disclosed in FIG. 2, the front segment 22 comprises a front wall 29 and side walls 30.

FIG. 3 is a schematic section view of the combustor front assembly of the FIG. 2 according to prior art along the section line A-A. In particular, FIG. 3 shows how the front segment 22 is coupled with the front plate 32 according the prior art. According to this embodiment, the combustor front assembly comprises a hook member 24 having a base 25 housed in a relative seat 26 realized in the front plate 32 and a hook end 27 configured to be coupled with a through slot 28 realized in the lateral wall 20 of the front segment 22. The hook member 24 is fixed and pushed against the front plate 32 by a screw or bolt member 31 in order to maintain the front segment 22 in the correct position.

However, the combustor front segment 22 are exposed to high level of vibrations and thermal deformation and, unfortunately, the foregoing described hook fixing system solution of the prior art is subject to frequent failure due to the high contact wear which leads often to disengage the front segments 22 from the combustor plate 32.

SUMMARY OF THE INVENTION

Accordingly, a primary object of the present invention is to provide a combustor front assembly for a gas turbine that allows to increase the lifetime and the reliability of the fixation and sealing system between the combustor front plate and the combustor front segments.

In order to achieve the objective mentioned above, the present invention provides a combustor front assembly for a gas turbine wherein the gas turbine comprises:

-   -   a rotor rotating around an axis;     -   a compressor upstream coupled to the rotor for compressing air;     -   a combustion chamber wherein the compressed air is mixed with         fuel and burnt in order to generate an high pressure gas;     -   a turbine downstream coupled to the rotor wherein the high         pressure gas expands performing rotating work on the axis.

Preferably, the combustion chamber comprising is an annular combustion chamber arranged concentrically to the turbine axis and comprises a combustor front assembly coupled with a plurality of burners, for instance EV-burners.

The combustor front assembly is provided with at least a though hole (a plurality of though holes in case of an annular combustion chamber) in order to allow the gas flow to leave the burners and to enter the combustion chamber. In particular, the combustor front assembly comprises:

-   -   a combustor front plate having at least a through hole and         provided with an outer surface outside the combustor chamber;         —at least a combustor front segment having a through hole and         coupled to the outer surface of the combustor front plate so         that the through hole of the front segment is aligned with the         through hole of the front plate.

According to the invention, the combustor front segment is clamped to the outer surface of the combustor front plate. In other words, according to the invention the combustor front segment is kept in position in abutment against the front plate in a clamped manner.

In case of an annular combustor, the combustor front assembly comprises a plurality of combustor front segments tile-shaped covering the entire outer surface of the combustor front plate.

Advantageously, the fixation system of the present invention, based on a clamping system between the front segment and the front plate, ensures robustness and reduces the risk of failure due front segment disengage during the start-up phase, the steady state operating regime and also after long operating periods.

In particular, each tile-shaped combustor front segments comprises a front wall, spaced and parallel to the outer surface of the combustor front plate, and two opposite L-shaped side walls. Each L-shaped side wall comprises a first portion, orthogonal to the outer surface of the combustor front plate and connected with the front wall, and a second portion spaced and parallel to the front wall facing the outer surface of the combustor front plate. This second portion of the side walls of the combustor front segments is clamped and forced against to the outer surface of the combustor front plate.

In particular, each tile-shaped combustor front segments comprises two side clamping strips having length equal to the side walls and are also configured to push the second portion of the side walls against the outer surface of the combustor front plate.

Advantageously, the clamping and pushing effects are acting along the entire length of the side wall and therefore the contact pressure is distributed over a large area. Consequently, this solution allows to reduce the risk of wear along the side walls of the front segment.

In particular, each tile-shaped combustor front segment comprises two side closing strips facing the side clamping strips and configured for clamping the free end of the second portion of the side walls between the side clamping strips and the side closing strips.

In particular, each tile-shaped combustor front segment comprises an L-shaped outer and inner wall having a first portion, orthogonal to the outer surface of the combustor front plate and connected with the front wall, and a second portion spaced and parallel to the front wall. The second portion of such outer and inner wall of the combustor front segments are clamped and pushed against the outer surface of the combustor front plate.

Advantageously, the clamping system of the present invention between the front segment and the front plate, ensure sufficient robustness also along the inner and outer walls.

In particular, each tile-shaped combustor front segment comprises an inner and an outer middle clamping plate arranged in the middle of the outer and inner wall. Such middle clamping plates are configured to clamp and push the second portion of the outer and inner wall against the outer surface of the combustor front plate. Also along the outer and inner wall each tile-shaped combustor front segment comprises an inner and outer closing strip. Each closing strip is facing the relative middle clamping plate for clamping the free end of the second portion of the outer and inner wall between the middle clamping plates and the inner and outer closing strip.

Advantageously, the clamping effect is acting along the entire length of the middle clamping plate and therefore the contact pressure is distributed over a large area. Consequently, this solution allows to reduce the risk of wear along the inner and an outer walls of the front segment.

In particular, the middle clamping plates are also in abutment against a step seat realized in the inner surface of the through hole of the front segment.

Advantageously, this solution allows to ensure the correct position of the middle clamping plates. Moreover, according to this feature, the front segment during the steady state operating condition is self-restraining due to its thermal deformation.

In particular, the inner and outer closing strip and the side closing strips are integral each-others to form a single square frame.

Advantageously, this solution allow to ensure an easy and quick assembly of the front segment.

In particular, the combustor front assembly comprises a seal between the combustor front segment and the outer surface of the combustor front plate. Preferably, the seal is a rope seal housed in a perimetric groove realized in the outer surface of the combustor front plate.

Advantageously, this solution allow the seal to be clamped in position with limited movements. Consequently, the seal lifetime is optimized.

In particular, the outer surface of the combustor front plate consists in straight portions.

Advantageously, such planar portions ensures to realize well-controlled clearances between the front plate and the front segments.

It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed. Other advantages and features of the invention will be apparent from the following description, drawings and claims.

The features of the invention believed to be novel are set forth with particularity in the appended claims.

BRIEF DESCRIPTION OF DRAWING

Further benefits and advantages of the present invention will become apparent after a careful reading of the detailed description with appropriate reference to the accompanying drawings.

The invention itself, however, may be best understood by reference to the following detailed description of the invention, which describes an exemplary embodiment of the invention, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic section view of a gas turbine provided with an annular combustion chamber;

FIG. 2 is a schematic partial prospective view of a front combustor assembly according to the prior art;

FIG. 3 is a schematic section view of the combustor front assembly of the FIG. 2 along the section line A-A;

FIG. 4 is a schematic partial prospective view of a front combustor assembly according to the invention;

FIG. 5 is a schematic section view of the combustor front assembly of the FIG. 4 along the section line B-B;

FIG. 6 is a schematic section view of the combustor front assembly of the FIG. 4 along the section line C-C;

FIG. 7 is a schematic partial prospective view of the combustor front assembly of the FIG. 4 under thermal deformation during the steady state operation regime of the relative gas turbine;

FIG. 8 is a schematic section view of the combustor front assembly of the FIG. 7 along the section line C-C;

FIG. 9 is a schematic section view of the combustor front assembly of the FIG. 7 along the section line D-D;

FIG. 10 is a schematic partial prospective view of the combustor front plate without any front segment according to the invention; and

FIG. 11 is a schematic exploded prospective view of the combustor front segment according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

In cooperation with attached drawings, the technical content and the detailed description of the present invention are described thereinafter according to preferable embodiments, being not used to limit its executing scope. Any equivalent variation and modification made according to appended claims is all covered by the claims claimed by the present invention.

In particular, reference will be made to the FIGS. 4-11 that disclose in detail an embodiment of the present invention. Reference to FIG. 1, that is a schematic view of a gas turbine, will be made only in order to explain how the invention cooperates with the relative gas turbine.

Reference in now made to the FIG. 4 that is a schematic partial prospective view of a front combustor assembly, on the burner side, according to the invention.

In particular, the FIG. 4 discloses a portion of a ring-shaped combustor front plate 34 centered around the turbine axis 4 (see also FIG. 1) and a tile-shaped combustor front segments 38 coupled to the outer surface 36 of the combustor front plate 34. The outer surface 36 is the surface of the front plate 34 that is outside the combustion chamber 7 facing the burner 11 (see also FIG. 1).

According to FIG. 4, the combustor front plate 34 is provided with a plurality of through holes 35 equally spaced whereas each combustor front segment 38 comprises a through hole 39. Once the combustor front segment 38 is coupled to the outer surface 36 of the combustor front plate 34, the through hole 39 of the front segment 38 is aligned with the through hole 35 of the front plate 34 in order to realize a passage for the gas flowing from the burner 11 to the combustion chamber 7. The front segments 38 are arranged along the front plate 34 in order to cover the entire outer surface 36.

According to FIG. 4, the front plate 34 comprises fixing portions 55 configured to couple the front plate 34 to the inner 13 and outer shell 14 of the combustion chamber 7 (see also FIG. 1). Each tile-shaped combustor front segment 38 comprises a front wall 40, side walls 41, an inner and an outer wall 46.

Reference is now made to FIG. 5 that is a schematic section view of the combustor front assembly of the FIG. 4 along the section line B-B.

According to FIG. 5, the front wall 40 of the front segments 38 is spaced and parallel with respect to the outer surface 36 of the front plate 34. The side walls 41 of the front segments 38 are L-shaped and comprise a first portion 42, orthogonal to the outer surface 36 of the combustor front plate 34, and a second portion 43, having a free end, spaced and parallel to the front wall 40. The second portion 43 of the side walls 41 of the combustor front segments 38 is facing the outer surface 36 of the front plate 34. The free end of such second portion 43 is clamped between the side clamping strip 44, in form of a rail parallel to the side wall 41, and the relative side closing strip 45. Respectively, the side clamping strip 44 is coupled with the inner surface (inside the front segment 38) of the second portion 43 of the side wall 41 of the combustor front segments 38, whereas the side closing strip 45 is coupled to the outer surface (facing the front plate 34) of the second portion 43 of the side wall 41 of the combustor front segments 38. By acting on a screw or bolt member 31 passing the front plate 34 and the side clamping strip 44 (see FIG. 5), the side clamping strip 44 allows to clamp the free end of the second portions 43 and to push the second portion 43 against the outer surface 36 of the combustor front plate 34. Indeed, as disclosed in FIG. 5, the side closing strip 45 are arranged in a lowered portion 56 of the outer surface 36 of the combustor front plate 34 so that the main part of the second portion 43 of the side wall 41 is in abutment against a perimetric higher portion 57 of the outer surface 36 of the combustor front plate 34. FIG. 5 discloses a seal 53 arranged in a groove 54 realized in the perimetric higher portion 57 of the outer surface 36 of the combustor front plate 34. In particular, the seal is between the outer surface 36 of the combustor front plate 34 and the second portions 43 of the side wall 41.

In view of the foregoing description, the front segment 38 can be defined as clamped against the front plate 34 because the free ends of the side walls 41 of the front segment 38 are clamped and pressed against the outer surface 36, in particular against the perimetric higher portion 57.

Reference is now made to FIG. 6 that is a schematic section view of the combustor front assembly of the FIG. 4 along the section line C-C.

FIG. 6 discloses that also the inner and outer wall of the front segment 38 are L-shaped and comprise a first portion 47, orthogonal to the outer surface 36 of the combustor front plate 34 and connected with the front wall 40, and a second portion 48. Such second portion 48 is spaced and parallel to the front wall 40 facing the outer surface 36 of the front plate 34.

As for the side walls 41, the free end of the second portion 38 of the outer and inner wall 46 is clamped between an inner and an outer middle clamping plate 49, arranged in the middle of the outer and inner wall 46, and an inner and outer closing strip 50. Acting on a screw or bolt member 31 passing the front plate 34 and the middle clamping plate 49 (see FIG. 6), the middle clamping plate 49 proceed with clamping the free and of the second portion 48, and push the second portion 48 against the outer surface 36 of the combustor front plate 34. According to FIG. 6, the middle clamping plate 49 is also resting on a step seat 52 realized in the inner surface of the hole 39. FIG. 6 also discloses a seal 53 arranged in a groove 54 realized in the perimetric higher portion 57 of the outer surface 36 of the combustor front plate 34. The seal 53 is placed between the outer surface 36 of the combustor front plate 34 and the second portions 48 of the inner and outer wall 46.

Reference is now made to FIGS. 7-9 that are schematic view of the combustor front assembly of the FIG. 4 during the steady state operation regime of the relative gas turbine. In other words, FIG. 7 discloses the combustor front assembly of the FIG. 4 under the operation thermal deformation. In particular, FIG. 8 and are schematic section views of the combustor front assembly of the FIG. 7 along the section lines C-C and D-D. These figures disclose that the clamping system of the present invention is self-restraining. Indeed, along the line C-C, i.e. at the inner or outer wall 46, the thermal deformation acting on the side clamping strips 44 generates an additional pushing force located at the clamping zone and at the step seat 52.

Along the line D-D, i.e. at the corner of the front segment 38, the thermal deformation generates an additional pushing force acting at the front segment 38 against the front plate 34. In FIGS. 8 and 9 the location where these additional pushing forces are acting have been schematically represented by the reference number 58. The dotted line 59 above the front wall 40 schematically represents the deformation of the front segment 38 during the steady state operation regime of the gas turbine.

Reference is now made to FIG. 10 that is a schematic partial prospective view of the combustor front plate 34 of FIG. 4 without the front segment 38. In particular, FIG. 10 discloses the lower portion 56 and the higher portion 57 of the outer surface 36 of the combustor front plate 34. According to the invention, these portions 56 57 of the outer surface 36 of the combustor front plate 34 are straight. Between the lower portion 56 and the higher portion 57, the outer surface 36 of the combustor front plate 34 comprises a step that realizes a seat for the seal 53.

Reference is now made to FIG. 11 that is a schematic exploded prospective view of the combustor front segment according to the invention. According to this embodiment, the inner and outer closing strip 50 and the side closing strips 45 are integral each-others to form a single square frame 51. According to FIG. 11, such square frame 51 is fixed in position with respect to the middle clamping plates 49 and to the side clamping strips 44 by bolt or screw 60.

Although the invention has been explained in relation to its preferred embodiment(s) as mentioned above, it is to be understood that many other possible modifications and variations can be made without departing from the scope of the present invention. It is, therefore, contemplated that the appended claim or claims will cover such modifications and variations that fall within the true scope of the invention. 

1. Combustor front assembly configured for a gas turbine power plant, wherein the combustor front assembly comprises: at least a through hole for allowing gas flow into a combustion chamber; a combustor front plate having at least a through hole and an outer surface outside the combustor chamber; and at least a combustor front segment having a through hole and coupled with the outer surface of the combustor front plate so that the through hole of the front segment is aligned with the through hole of the front plate; wherein the combustor front segment is clamped in position and forced against the outer surface of the combustor front plate.
 2. The combustor front assembly as claimed in claim 1, in combination with a gas turbine which comprises: a rotor having an axis, the combustor front plate being ring-shaped around the axis; the combustor front plate including a plurality of through holes equally spaced along the front plate; and the combustor front assembly including a plurality of combustor front segments which are tile-shaped, covering an entire outer surface of the combustor front plate.
 3. The combustor front assembly as claimed in claim 2, wherein each combustor front segments comprises: a front wall spaced and parallel to the outer surface of the combustor front plate; and two opposite side walls which are L-shaped, having a first portion, orthogonal to the outer surface of the combustor front plate and connected with the front wall, and a second portion spaced and parallel to the front wall, the second portion of the side walls of the combustor front segments being clamped and pushed against the outer surface of the combustor front plate.
 4. The combustor front assembly as claimed in claim 3, wherein each combustor front segment comprises: two side clamping strips having lengths equal to the side walls acting on the second portion of the side walls inside the combustor front segments.
 5. The combustor front assembly as claimed in claim 4, wherein each combustor front segment comprises: two side closing strips facing the side clamping strips for clamping a free end of the second portion of the side walls between the side clamping strips and the side closing strips.
 6. The combustor front assembly as claimed in claim 1, wherein each combustor front segment comprises: a front wall spaced and parallel to the outer surface of the combustor front plate; an outer wall and an inner wall, each L shaped and having a first portion, orthogonal to the outer surface of the combustor front plate and connected with the front wall, and a second portion spaced and parallel to the front wall; the second portion of the outer and inner walls of the combustor front segment being clamped and pushed against the outer surface of the combustor front plate.
 7. The combustor front assembly as claimed in claim 6, wherein each combustor front segment comprises: an inner clamping plate and an outer clamping plate arranged in a middle of the outer and inner walls acting on the second portion of the outer and inner walls inside the combustor front segments.
 8. The combustor front assembly as claimed in claim 7, wherein each of the combustor front segments comprises: inner and outer closing strips facing the inner and an outer clamping plates for clamping a free end of the second portions of the outer and inner walls between the clamping plates and the inner and outer closing strips.
 9. The combustor front assembly as claimed in claim 8, wherein the clamping plates are in abutment against a step seat realized in an inner surface of the through hole of the front segment.
 10. The combustor front assembly as claimed in claim 8, wherein the inner and outer closing strips and the side closing strips are integral each other to form a single square frame.
 11. The combustor front assembly as claimed in claim 1, comprising: a seal between the combustor front segment and the outer surface of the combustor front plate.
 12. The combustor front assembly as claimed in claim 11, wherein the seal is a rope seal housed in a perimetric groove realized in the outer surface of the combustor front plate.
 13. The combustor front assembly as claimed in claim 11, wherein the outer surface of the combustor front plate is formed of straight portions.
 14. A gas turbine power plant in combination with the combustor front assembly as claimed in claim 1, the gas turbine power plant comprising: a rotor arranged for rotating around an axis; a compressor coupled to the rotor and arranged in an upstream location for compressing air; an annular combustion chamber configured for mixing compressed air with fuel and burnt in order to generate an high pressure gas; and a turbine arranged in a downstream location if the rotor and coupled to the rotor wherein high pressure gas will expand performing work on the rotor, the annular combustion chamber being arranged concentrically to the axis and including a combustor front assembly coupled with a plurality of burners.
 15. Gas turbine power plant as claimed in claim 14, wherein the burners are EV-burners or AEV-burners.
 16. A gas turbine power plant in combination with the combustor front assembly as claimed in claim 5, the gas turbine power plant comprising: a rotor arranged for rotating around an axis; a compressor coupled to the rotor and arranged in an upstream location for compressing air; an annular combustion chamber configured for mixing compressed air with fuel and burnt in order to generate an high pressure gas; and a turbine arranged in a downstream location if the rotor and coupled to the rotor wherein high pressure gas will expand performing work on the rotor, the annular combustion chamber being arranged concentrically to the axis and including a combustor front assembly coupled with a plurality of burners.
 17. A gas turbine power plant in combination with the combustor front assembly as claimed in claim 9, the gas turbine power plant comprising: a rotor arranged for rotating around an axis; a compressor coupled to the rotor and arranged in an upstream location for compressing air; an annular combustion chamber configured for mixing compressed air with fuel and burnt in order to generate an high pressure gas; and a turbine arranged in a downstream location if the rotor and coupled to the rotor wherein high pressure gas will expand performing work on the rotor, the annular combustion chamber being arranged concentrically to the axis and including a combustor front assembly coupled with a plurality of burners. 